1. Field of the Invention
The invention relates to a transmission mechanism with the function of the shock absorption, and more particularly to a transmission mechanism in which an adjusting unit is installed.
2. Description of the Related Art
As shown in FIG. 1, a conventional treadmill 60 includes a base frame 61 on which a platform 62 is mounted. A running board 63 and a continuous moving belt 64 are placed on the platform 62. In order to enhance the comfort in operating the treadmill 60, the running board 63 has a shock-absorbing effect. The most common shock-absorbing design is either to interpose a shock-absorbing element like cushioning pad between the running board 63 and the base frame 61 or to place a cushioning layer (not shown) on the surface of the running board 63 for achieving the cushioning effect of the continuous moving belt 64. However, this design has problems of incomplete integrity and inadequate shock absorption. The reason for that lies in that the platform 62 and the running board 63 are still rigid in spite of the cushioning pad or the cushioning layer thereon. The reactive force of the running board 63 acting on the feet is great when the operator walks on the continuous moving belt 64. In addition to the discomfort, a long-term use of this kind of treadmill will cause exercise injuries.
Besides, a transmitting mechanism having a lifting effect is often available between the platform 62 and the base frame 61 for adjusting the angle of elevation of the platform 62 with respect to the horizontal, thereby meeting different requirements of the operators. This transmitting mechanism (or so-called lifting motor) has to match different space and lifting mechanism. As shown in FIGS. 2A and 2B, a transmitting mechanism 70 has one end pivotally coupled to a protruding ear 611 of the base frame 61 and the other end pivotally coupled to an actuating piece 651 of the drive lever 65. In retracting a transmission rod 72 by a motor 71, the drive lever 65 rotates on a pivoting portion 652, thereby forcing a lifting rod 66 in a raised position. The angle θ of the elevation of the platform 62 including the running board can be adjusted in a pulling (retracting) way. As shown in FIGS. 3A and 3B, the pivoting position between the transmission rod 72 and the drive lever 65 is different from the above-mentioned embodiment. The angle θ of the elevation of the platform 62 is, on the contrary, adjusted in a pushing (extending) way. From the aforementioned descriptions, the angle θ of the elevation of the platform 62 is adjustable in the pulling (retracting) or pushing (extending) way according to the lifting mechanism. No matter which way is applied, the whole structure of the transmitting mechanism 70 is still a rigid configuration which does not contribute to the shock-absorbing effect of the platform 62. Meanwhile, the transmitting mechanism 70 is fitted to the structure such that an additional cushioning mechanism is not able to be added to the platform 62. Accordingly, the shock-absorbing effect of the conventional treadmill has not improved yet.